从带有其他列的表中选择不同的值

Question

我有以下SQL（请注意使用distinct）：

SELECT DISTINCT
    question_id AS id,
    question_id AS object_id,
    created_at AS created,
    created_at AS lastmessage,
    'T' AS object_type
FROM
    responses

...这给了我...

我想摆脱第一列中的重复行。我想念什么？

Answer 1

如果要每行一行，请使用聚合。像这样：

SELECT question_id AS id, question_id AS object_id,
       MIN(created_at) AS created,
       MAX(created_at) AS lastmessage,
       'T' AS object_type
FROM responses
GROUP BY question_id;